1. Field of Invention
The invention relates to an adjusting method and an adjusting device, in particular, to an adjusting method and an adjusting device of adjusting sensitivity of signal interpretation in the field of fan control.
2. Related Art
A conventional fan system is typically driven by an electronic system, wherein the fan system has a controller or a control chip, and the controller or the control chip generates a control signal to control a rotating speed of a fan according to a change of a duty cycle of a pulse width modulation (PWM) signal, which is continuously inputted by the electronic system.
Referring to FIG. 1, a conventional fan system 1 electrically connected to an electronic system 2 of a client includes a fan 11 and a controller 12. The electronic system 2 continuously inputs a pulse width modulation signal PWM to the controller 12 to control a rotating speed of the fan 11. The fan system 1 rapidly and continuously samples the pulse width modulation signal PWM in a fixed manner to detect the continuity and the stability of the pulse width modulation signal PWM as a reference for judging the system state. As shown in FIG. 2A, the typical pulse width modulation signal PWM has a rectangular wave with a constant cycle T. However, when the fan system 1 operates in different environments with different noises, the endurance against the noises is not completely kept unchanged. The noises can be easily inputted together with the pulse width modulation signal PWM, as shown in FIG. 2B. The pulse width modulation signal PWM is interfered by the noises so that the waveform is changed to cause the miss step (MS) phenomenon, for example. Therefore, when the fan system 1 samples the pulse width modulation signal PWM, mis-judgment may be made to cause the malfunction.
Because the operating environment of the fan system 1 is changing, the sensitivity of signal interpretation is influenced if the endurance against the noises cannot be adjusted correspondingly. Furthermore, the fan system 1 itself cannot judge whether the pulse width modulation signal PWM has the noise N or not. So, when this condition occurs, the rotating speed of the fan 11 is unstable, the operation of the fan system 1 is influenced, and the heat dissipating efficiency is deteriorated.